Malware, also known as malicious software, is code designed to infect a system, steal information, enslave computers and potentially damage systems -- as well as replicate itself and spread to new victims.
From spyware to Trojans, keyloggers to viruses and worms, the list of malware types is endless -- and more is being found in the wild every day which affects different operating systems and devices. Some will replicate and spread, others will hide themselves away in a PC and spy on you, and other types of malware want your financial information.
You may have pop-up windows and adverts, your PC may have slowed down, and in severe cases may not work at all.
The image above shows a kind of ransomware. The malicious code locked the PC and displayed this sign, pretending to be law enforcement and demanding payment to decrypt the computer's files.
Read on: The ransomware guide
Malware is a broad term, and many things could happen - your computer may end up a slave unit in a botnet and used to send spam, you may be spied upon through your webcam and keystrokes, and your system may be damaged permanently if files are corrupted. You might also be held to ransom.